Magnetic and anisotropy and electronic transport properties insingle-crystalline compounds of EuCu2G2 and EuCu2Si2

Abstract

We present the temperature dependent magnetization, M(T), and the resistivity, rho(T), of EuCu2Ge2 and EuCu2Si2 in single crystalline form. The EuCu2Ge2, which is synthesized in single-crystalline form, shows two different magnetic transitions in M(T) at T-Mc=8.5 K and T-Mab=4 K depending upon the magnetic field orientation. On the other hand, the rho(T) reveals only one transition at T=4 K as a sudden drop of the rho(T) without any noticeable change at T=8.5 K. For the EuCu2Si2, M(T) shows a two step antiferromagnetic transition at T(N1)approximate to10 K and T(N2)approximate to4 K, which is smeared out under Hgreater than or equal to1 T, probably due to field induced spin orientation. The transition at T-N2 is also manifested as a decrease in rho(T) due to loss of magnetic scattering. Interestingly, another exotic transition is found at T=2 K in rho(T) data. The rho(T) values rapidly increase by two orders of magnitude from rho=20 muOmega cm at T=2 K and reach rho=5 mOmega cm at T=0.5 K, which is similar to a metal-insulator transition. (C) 2003 American Institute of Physics.